Conventionally, this type of high-frequency heating cooker (e.g., microwave oven) is configured to heat a heating-target object such as a food placed inside a heating chamber by a high-frequency generator such as a magnetron. In the conventional high-frequency heating cooker, it is possible that, by an excessive heating of the heating-target object, the heating-target object burns, the temperature of the heating chamber is raised to an abnormal temperature, flames spread to the outside of the high-frequency heating cooker, and a fire breaks out.
FIG. 7 is a perspective view of an internal structure of the high-frequency heating cooker of a first conventional example (see, e.g., Patent Document 1: Japanese Unexamined Patent Publication No. 1987-299624). As shown in FIG. 7, in the high-frequency heating cooker of the first conventional example, an excessive temperature rise preventing device 104 such as a temperature switch is disposed at an end on the exhaust opening 103 side of a top plate 102 of a heating chamber 101. This excessive temperature rise preventing device 104 detects an abnormal temperature rise inside the heating chamber 101 and breaks a power supply to a high-frequency generator (not shown), thereby preventing flames from spreading to the outside of the high-frequency heating cooker.
FIG. 8 is a perspective view of the internal structure of the high-frequency heating cooker of a second conventional example. The high-frequency heating cooker of the second conventional example, as an apparatus that heats the heating-target object, has a heater 105 in addition to the high-frequency generator (not shown). The heater 105 has its heating part disposed along the inner surface of the top plate 102 so that it can bake the surface of the heating-target object placed inside the heating chamber 101.
In the case of disposing the heater 105 on the top plate 102, the temperature of the top plate rises rapidly when the heater 105 is energized. For this reason, when the excessive temperature rise preventing device 104 is disposed on the top plate 102, the excessive temperature rise preventing device 104 can erroneously detect the temperature rise of the top plate 102 as the abnormal temperature rise inside the heating chamber 101.
For this reason, in the high-frequency heating cooker of conventional example 2, the excessive temperature rise preventing device 104 is disposed on an exhaust guide plate 106 with its upper end fixed to the top plate 102 of the heating chamber 101 to face the exhaust opening 103. This sets the excessive temperature rise preventing device 104 apart from the heater 105, preventing an erroneous detection of the excessive temperature rise preventing device 104. Sensitivity of the excessive temperature rise preventing device 104 is enhanced by disposing it in the vicinity of the exhaust opening 103. To suppress the temperature rise of a side plate of a housing of the high-frequency heating cooker, the exhaust guide plate 106 guides the air discharged from the exhaust opening 103 not to hit the side plate directly.